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United States Department of Agriculture

Agricultural Research Service

Title: Germination Requirements Vary in Wild Rubus Species

Author
item Wada, Sugae
item Reed, Barbara

Submitted to: HortScience
Publication Type: Abstract Only
Publication Acceptance Date: 4/17/2008
Publication Date: 6/14/2008
Citation: Wada, S., Reed, B.M. 2008. Germination Requirements Vary in Wild Rubus Species. HortScience. 43:1272.

Interpretive Summary: Seeds of blackberry and raspberry (Rubus) are difficult to germinate because of a hard seed coat that causes dormancy. To better define the germination requirements of wild species, we examined the effect of two chemicals, a concentrated acid and a concentrated base, for degrading the seed coat of 6 wild species. After chemical treatment, the seeds were germinated with 4 weeks warm (18 oC) followed by 12 weeks cold (4 oC) in the presence of four types of germination treatments. Fresh untreated seed of one species had 14.5% germination, but untreated fresh seed of the other 5 species did not germinate. One species had very poor germination with all treatments. Most acid-treated seed germinated by 6 months with a few additional seeds germinating by 12 months. Germination was poor six months after base treatment, but significantly improved by 12 months for 5 of 6 species. Despite the increased germination at 12 months, base treatment produced significantly less germination than sulfuric acid for 4 of the 6 species. Germination treatments following acid treatment produced >50% germination for 5 of the 6 species by 6 months. Germination treatments following base treatment were dependent on the species. This study indicates that Rubus species vary in their germination requirements with one exhibiting low dormancy and one very deep dormancy while the others had moderate dormancy.

Technical Abstract: Seeds of blackberry and raspberry have a deep dormancy caused by one or more mechanisms. Rubus seeds are normally enclosed in a hard endocarp that is a major constraint for their germination. To better define the germination requirements of wild species we examined the effect of two scarification agents, concentrated sulfuric acid (98% +) and sodium hypochlorite (14%), on the seed of three species in subg. Rubus: R. ursinus Cham. & Schltdl., R. georgicus Focke, R. caesius L.; and three species in subg. Idaeobatus: R. hoffmeisterianus Kunth & C. D. Bouché, R. coreanus Miq., R. occidentalis L. After scarification, the seeds were germinated with 4 weeks warm (18 oC) followed by 12 weeks cold (4 oC) stratification in the presence of either water, GA3, GA3 and KNO3, or smoke treatments. Fresh untreated R. caesius seed had 14.5% germination, but untreated seed of the other 5 species did not germinate. R. occidentalis had poor germination with all treatments (<8%). One month after sulfuric acid treatment and warm stratification, germination was 67% of R. hoffmeisterianus seeds; 4 % of R. coreanus, 6% of R. georgicus, 12% of R. caesius and none of R. occidentalis and R. ursinus. . Most sulfuric acid scarified seed germinated by 6 months with a few more by 12 months. Germination was poor six months after sodium hypochlorite scarification, but significantly improved by 12 months. Despite the increased germination at 12 months, sodium hypochlorite scarification produced significantly less germination than sulfuric acid for four of the six species. Germination treatments following sulfuric acid scarification produced >50% germination for five of the six species (not R. occidentalis) by 6 months. This study indicates that Rubus species vary in their germination requirements with R. hoffmeisterianus exhibiting low dormancy and R. occidentalis very deep dormancy, while the others had moderate dormancy.

Last Modified: 09/25/2017
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